Lady Gaga And Tony Bennett Sing "The Lady Is A Tramp" For President Obama

Lady Gaga teamed up with legendary crooner Tony Bennett to sing at a private event for Obama's staffers.

The eccentric performer, who wowed in a white Versace dress, belted out "The Lady Is A Tramp" alongside Bennett at the Washington Convention Center.

When President Obama hit the stage, his staffers reportedly sang to him ... "Signed, Sealed, Delivered."

Looks like it was quite the night!